Common practice in surgical anastomosis consists in the use of stitches applied to the vessel's wall. Many attempts have been made to make anastomosis without stitches (sutureless). These particular techniques are called "mechanical anastomosis." They are based on the concept of folding the vessel's walls together ("wall eversion") and fasten them by a mechanical device. After about 10 years of research, this type of anastomosis has not been proven successful enough to be performed on human beings. The main problem experienced with "wall eversion" is the atrophy of the vessel walls folded together. The atrophy occurs because in the part of the wall that is folded (everted wall), the blood flow is significantly reduced.
Several particular techniques have been developed for sutureless repair of vessels. These techniques can be summarized in the following four categories:
a) stapling devices; b) metal rings ("Nakayama rings" and "Unililink" systems); c) heat-shrink tubing; and d) absorbable couplers.
The objective of all of these techniques has been to improve reliability, reduce required execution time and provide a less technically demanding procedure than the standard suturing together of the ends of severed blood vessels.
However, in order to avoid blood clots, all these techniques must rely on the principle of vessel wall eversion. This consists in folding the vessel's wall in a way that the inner part of the two vessels, called "intima", are smoothly abutting as shown (in FIG. 13 ref.: D. E. Mattox, J. J. Wozniak: "Sutureless Vascular Anastomosis with Biocompatible Heat-Shrink Tubing"; Arch Otolaryngol Head Neck Surg--November 1991, vol 117: 1260-1264). This technique reduces the risk of blood clotting, called thrombosis, by positioning the outer part of the vessel wall, called "adventitia" outside of the vessel area exposed to blood flow called "lumen".
The drawback of the above techniques is that once the vessel is folded, the inner part of vessel layers, called "intima", is no longer in contact with the blood flow through the vessel. This condition, as shown in several scientific papers (K. Nakayama, 1962; PI. Androsov, 1956; R. K. Daniel et al., 1984; J. J. Wozniak, 1985; L. T. Ostrup, 1986 and D. E. Mattox, 1991), and especially when applied to small diameter vessels, could cause the atrophy of the vessel wall involved in the suture. On the other hand, large diameter vessels, are not suitable for mechanical anastomosis because the vessel wall tends to rupture when folded.